As is generally well known, most prior art railroad coupler assemblies are relatively complicated. These coupler assemblies, in addition to rather complex coupler connections and associated components, normally include a draft gear or some other shock absorbing device which are provided to cooperate with the connection between the coupler components and the railroad car center sill to prevent damage to both lading and equipment.
The draft gear assemblies are positioned to receive the linear impact loads incidental to train movements and coupling activity. These draft gear assemblies function to absorb and dissipate the forces generated during such train movements. While draft gear assemblies originally consisted primarily of heavy compression springs, current day draft gear structures are of various types. Modern draft gear assemblies include friction draft gears, hydraulic draft gears, rubber draft gear, combination friction-rubber draft gear and others. All of these draft gears are designed to permit some form of compressive reaction in response to sudden buff or draft loading which will compress the draft gear to absorb and dissipate the impact energy. Accordingly, such conventional railway car coupler arrangements have a degree of both free and cushioned slack. That is, there is a certain amount free "play" between the coupler components and the center sill member when the load changes from a draft to a buff load, and vice versa.
More recently, however, research has indicated that the elimination of the free and cushioned slack within a train consist can result in the substantial elimination of over the road train forces due to "run-ins" and "run-outs". The magnitude of these train forces are normally quite large. Furthermore, these train forces can cause significant wear and tear on the rolling stock. In some instances, these forces may even be severe enough to be a contributing factor in bringing about a derailment of at least a portion of the train consist. Specifically, in conventional coupler assemblies, the draft key or pin connection of the coupler to the yoke is at a relatively long distance from the kingpin about which the car truck is free to rotate. The negotiation of curves, particularly under buff loading conditions, can give rise to relatively large lateral forces being generated. These large lateral forces can be particularly damaging to the coupling and draft gear equipment
Also, as is well known in the railway art, a conventional draft gear assembly is provided with some form of compression member. Such compression member is positioned to reciprocate linearly and substantially parallel to the center sill to absorb and dissipate the linear forces. Accordingly, any lateral forces which may be created will often tend to twist or bend the moving elements thereby establishing conditions which can contribute to damage of the draft gear assembly.
As is likewise known, drawbar-type coupler assemblies are particularly adapted for use in unit train applications. In a unit train, the railway cars are normally coupled and uncoupled only for periodic maintenance and repair. Such cars usually are not subjected to routine impact forces associated with bumping encountered in classification yards and, therefore, do not require heavy duty cushioning provided by conventional prior art draft gear assemblies.
More recently, slackless rotary drawbar coupler assemblies have been developed. Such slackless rotary drawbar couplers utilize a gravity wedge to maintain the slackless connection against the spherical or hemispherical drawbar end connection. In view of the fact that such cars making up a unit train are not normally subjected to the high impact forces associated with bumping encountered in classification yards, many of the slackless rotary drawbar couplers have eliminated the use of draft gear assemblies altogether.
In the case of retrofitting existing railroad cars with the newer slackless rotary drawbar couplers, however, it has been found that it is not normally possible to eliminate the draft gear assembly normally positioned in the draft gear pocket of a standard coupler without completely reconstructing the center sill member to eliminate the draft gear pocket. Accordingly, in retrofitting existing railway cars with the newer slackless drawbar couplers, the common practice has been to either utilize conventional draft gear, or fill the draft gear pocket with a solid structure fabricated of steel plate stock to absorb whatever impact forces are created without utilizing moving compressible members. Such fabricated structures, are commonly referred to as a blockout draft gear. These blockout draft gear are, nevertheless, subjected to rather high impact loading when the load changes from draft to buff loading, or vice versa, and have, therefore, always been very heavy structures. Such structures being fabricated of heavy plate steel members in a variety of complex configurations as essential to absorb the loads encountered. While such fabricated blockout draft gear may be more simplified in structure than conventional draft gear with compressible members, prior art blockout draft gear are still rather complicated in structure. For example, such blockout draft gear will often require that the receiving pocket be modified to facilitate their use. One common prior art blockout device for a draft gear pocket is a form fabricated from a section of heavy seamless steel pipe, normally having a wall thickness of more than one inch, welded between a pair of heavy steel end plates, and having a plurality of elongated heavy steel ribs welded to, and spaced around the periphery of the pipe section. Such prior art blockout device for draft gear assembly pockets are time consuming and rather costly to produce.